Every puzzle we serve is machine-verified
We don't just hope our puzzles are fair — we prove it, with a solver that runs independently of the puzzle generator. Below is the real data behind each guarantee badge, and how to reproduce it yourself.
FreeCell — 99.9992% of deals are winnable
We number our deals exactly like Microsoft's original FreeCell (1 to 1,000,000), so every game lines up with decades of FreeCell records. Of the first million deals, only 8 can never be won — and our own solver proves each one unsolvable by exhausting the entire game tree. We never serve them: every deal in rotation is triple-checked (deal → solve → replay).
Deal #11982 — the most famous unsolvable FreeCell game — is proven unsolvable in 61,643 search nodes.
| Deal # | Nodes to prove unsolvable |
|---|---|
| #11982 | 61,643 |
| #146692 | 8,637 |
| #186216 | 16,606 |
| #455889 | 11,806 |
| #495505 | 27,688 |
| #512118 | 22,490 |
| #517776 | 67,016 |
| #781948 | 4,381 |
We currently serve 768 verified deals — 0 unsolvable, 0 unverified.
Minesweeper — no guessing, ever
Every board can be cleared by pure logic from the first click. No 50/50 coin-flips. We generate candidate boards and reject any that would force a guess — on Expert, that means rejecting about 89% of them.
| Difficulty | Boards that would force a guess (rejected) |
|---|---|
| Easy 9×99×9 / 10 | 7% |
| Medium 16×1616×16 / 40 | 38.8% |
| Hard 30×1630×16 / 99 | 89% |
100% · No guessing — solvable by logic alone ✓
Nonogram — exactly one solution
Every picture has a single unique solution you can reach by line-by-line logic alone. Counter-intuitively, small grids are the hardest to make unique — we reject about 88% of 5×5 candidates.
| Size | Candidates without a unique line-logic solution (rejected) |
|---|---|
| Easy 5×55×5 | 87.6% |
| Medium 10×1010×10 | 68.9% |
| Hard 15×1515×15 | 49.6% |
100% · Single solution — solvable by logic alone ✓
Water Sort — the "par" is the true minimum
Every level is solvable, and the par we show is the exact fewest possible moves — proven by an A* solver, not estimated. Harder levels need more: Hard runs 21–35 moves.
| Difficulty | Fewest moves (proven optimal) |
|---|---|
| Easy (7 tubes)5 colors / 7 tubes | 8–16 (avg 11.8) |
| Medium (10 tubes)8 colors / 10 tubes | 15–23 (avg 18.8) |
| Hard (14 tubes)12 colors / 14 tubes | 21–35 (avg 26.9) |
100% · Every board solvable — optimal moves shown ✓
How to check this yourself
Two rules keep these guarantees honest. First, the solver is independent of the generator — a generator never grades its own work. Second, everything is reproducible: run node scripts/guarantee-stats.mjs and you'll get the same proof sizes. Every solver is open in our codebase.
Data generated 2026-07-26.
Frequently asked questions
Are all FreeCell games winnable?
Almost all. Of the first 1,000,000 numbered deals, exactly 8 are unsolvable — about 99.9992% are winnable. We prove all 8 unsolvable with our own solver and never serve them.
Which FreeCell deals are impossible to win?
In the first million: #11982, #146692, #186216, #455889, #495505, #512118, #517776 and #781948. #11982 is the only unsolvable deal among Microsoft's original 32,000.
What does no-guess Minesweeper mean?
Every board can be solved by logic alone — you never reach a spot where two cells are equally likely to be a mine and you must guess. Boards that would force a guess are rejected before we serve them.
Does every Nonogram have a unique solution?
Yes. Each puzzle is verified to have exactly one solution, reachable by line-by-line logic — so you never need to guess or backtrack from a wrong branch.
Is the Water Sort move count the real minimum?
Yes. The par is computed by an exact A* solver as the provably fewest moves for that level, not an approximation.